As a protocol that makes a route in Layer 2 of an open systems interconnection (OSI) reference model redundant, there is transparent interconnection of lots of links (TRILL). TRILL has features of effective utilization of a frequency bandwidth, high speed switching upon failure and so forth in comparison with spanning tree protocol (STP).
It is to be noted that there is a technology which provides a routing controlling unit in an environment in which a network that transfers a packet along a route indicated from an upper apparatus and another network that performs routing control of the autonomous control type are coupled to each other. In the technology, a communication system includes a first switch that performs information exchange with adjacent switches by a given routing protocol to generate a transfer table and refers to the transfer table to transfer a packet. The communication system further includes a second switch that transfers a packet in accordance with an instruction from a given controller, a controller that issues an instruction to the second switch, and an integrated controller.
The integrated controller issues, to the controller, a packet transfer instruction along a designated route to the second switch and an instruction to generate a virtual network configured from switches that virtualize the first switch to the controller. Then, the integrated controller causes the controller to perform information exchange by a given routing protocol between the second switch and the first switch mapped to the virtual network such that packet transfer is performed along a route calculated in advance. As a related art, for example, there is Japanese Patent No. 5950019.